RE: motor oil
As far as switching to a synthetic oil, it will not hurt the engine by no means. But say you have 150,000 miles on the engineor 5,000 it will not cause nothing but if you have an oil leak, even it it only drips once per day, the synthetic will make the leak worse as the particles in the oil break up. So no there will be no problem caused but it will bring up existing that you didn't know about. Hope that helps.
Brandon